Contactless communication with authorization by human contact and visual indicator

ABSTRACT

Transponder comprising a resonant circuit, comprising an antenna and a capacitor, and at least one memory, wherein it comprises at least one contact zone for receiving a portion of human body, so that the positioning of a portion of human body on a contact zone modifies the electric circuit of the transponder, capable of switching from a first state in which it does not allow the memory to be read and/or written to a second state in which it allows the memory to be read and/or written when the resonant circuit of the transponder is contactlessly powered by a reader and in that it comprises an indicator which makes it possible to indicate that the positioning of a portion of human body on the contact zone of the transponder is or has been recognized.

BACKGROUND

1. Technical Field

The present document relates to an electromagnetic transponder, that isto say a transmitter-receiver device capable of interchanging datacontactlessly and wirelessly. It also relates to a system comprising acontactless reader and such a transponder. It is particularly suitablefor a transponder with no standalone power supply, of the contactlessintegrated-circuit card type. Finally, it relates to a secure method ofcontactless data interchange based on such a transponder.

2. Description of the Related Art

Certain contactless portable objects, such as certain integrated circuitcards called contactless cards, operate by remote power supply, in otherwords by contactless power supply. Such an object is activated in thepresence of a certain electromagnetic field produced and sent by areader with which it is supposed to communicate. Hereinafter it will besaid that such an object is powered contactlessly by a reader when it isin the electromagnetic field generated by a reader, at its resonancefrequency. Such an electromagnetic field transmits to the object theenergy for the object to operate while conveying the data interchangedwith the reader, during a communication called a radiofrequencycommunication, or more simply called contactless communication, asopposed to the communications that require a physical electrical contactwith a reader via an electrical connector.

An electromagnetic field is therefore used both for powering such acontactless object and for establishing a communication between a readerand the contactless object. Since such a communication is establishedwithout physical contact between the two communicating devices, there isa risk that a reader enters into communication with a contactlessportable object without the knowledge of its owner, for fraudulentpurposes or simply by accident. This risk is very problematic becausesuch contactless objects often contain sensitive data such as dataassociated with the private life of its owner, and can be used forapplications in which great security is desired, such as the medium forpersonal information in a passport, a health card, or for makingelectronic payments.

The contactless portable objects may therefore be subjected to maliciousattacks for the purpose of gathering personal information from theirowner, or for carrying out operations such as electronic signatures orelectronic payments without their knowledge. This risk is all thegreater if the carrier of the contactless object has no means ofdetecting the presence of the electromagnetic field of the reader and nomeans of knowing that his object is in the process of carrying out acontactless communication.

To reduce the risk explained above, document U.S. Pat. No. 6,588,660describes a contactless integrated circuit card, also called smart card,furnished with an antenna, the structure of which makes it inactive atthe usual resonance frequency of contactless smart cards. This cardfurther comprises a housing designed so that a user places his finger inorder to create an effect that then modifies the properties of theantenna, more precisely its internal interference parasite capacitor,and consequently its resonance frequency, so that it becomes activatableat the usual and standardized communication frequencies of contactlesssmart cards. This solution is therefore meant to prevent frauds since anintentional action of the holder of the contactless smart card isnecessary to allow the card to be powered and to operate normally.However, such an approach has several drawbacks. First, the effectobtained by the placing of a finger on the housing provided on the cardis very variable; notably it depends on the ambient humidity and onindividuals. In point of fact, the resonance frequency of the antenna ofthe card depends precisely on its capacitance. The result of this isthat the real resonance frequency of such a card after the placing of afinger on the housing provided remains imprecise and variable and theperformance of such a card is greatly compromised because of thisuncertainty, which might make it difficult or even impossible to use incertain conditions. Moreover, there are attacks which consist inattempting a communication with a transponder by scanning severalfrequencies until a response is obtained from the transponder. Such asmart card remains totally vulnerable to such attacks.

Thus, there is a need for a contactless communication solution that doesnot comprise all or some of the drawbacks mentioned above.

More precisely, there is a first need for a solution allowing a secureand reliable contactless communication.

Moreover, there is a second need for a solution allowing a contactlesscommunication of little bulk, compatible with use within an integratedcircuit card, of small dimensions like the format of a bank card asstandardized.

BRIEF SUMMARY

Accordingly, one embodiment of the disclosure is based on a transpondercomprising a resonant circuit, comprising an antenna and a capacitor,and at least one memory, characterized in that it comprises at least onecontact zone for receiving a portion of human body, so that thepositioning of a portion of human body on a contact zone modifies theelectric circuit of the transponder, capable of switching from a firststate in which it does not allow the memory to be read and/or written toa second state in which it allows the memory to be read and/or writtenwhen the resonant circuit of the transponder is contactlessly powered bya reader and in that it comprises an indicator which makes it possibleto indicate that the positioning of a portion of human body on thecontact zone of the transponder is or has been recognized.

The transponder may comprise a second indicator which makes it possibleto indicate that the transponder is contactlessly powered by a reader.

The two indicators may form a single indicator.

The indicator may be a visual indicator of the light-emitting diodetype.

The transponder may comprise an indicator, in series with a firstswitch, between the two terminals, the high terminal and the lowterminal of the transponder, and two resistors in series on a parallelbranch between the two terminals, the high terminal and the low terminalof the transponder, of which one terminal of intermediate potential,positioned between the two resistors, is connected to the first switchin order to drive its opening or its closure, and it may comprise asecond switch placed between the intermediate terminal and thelow-voltage terminal of the transponder.

The indicator may be in series with an electric channel linked to thecontact zone.

The resonant circuit may have characteristics that allow it to bepowered contactlessly around an activation frequency, this activationfrequency remaining the same in both states of the transponder.

The resonant circuit may begin to resonate and induce a voltagedifference between its high terminal and low terminal when thetransponder is contactlessly powered by a reader, in both states of thetransponder.

The at least one memory may be connected to the resonant circuit by anintermediate circuit, the at least one contact zone for receiving aportion of human body being on the intermediate circuit.

The transponder may comprise a contact zone comprising a contact pad onwhich the positioning of a portion of human body has a capacitiveeffect, or comprising two adjacent contact pads on which the positioningof a portion of human body has a resistive effect.

The transponder may comprise at least one contact zone on which simplythe contact of a portion of human body is sufficient for the switch fromits first state to the second state when its resonant circuit iscontactlessly powered by a reader, or the transponder may always be inthe first state when no portion of human body is placed on its at leastone contact zone and in the second state when a portion of human bodyremains placed on its contact zone and its resonant circuit iscontactlessly powered by a reader.

The transponder may be a contactless or dual integrated circuit card.

The disclosure also relates to a telephone incorporating a transponderas described above.

The disclosure also relates to a system comprising a reader comprising acircuit oscillating at a resonance frequency, characterized in that itcomprises a transponder as described above of which the resonant circuithas a resonance frequency tuned to that of the reader.

The disclosure also relates to a method of contactless communicationbetween a reader and a transponder as described above, characterized inthat it comprises the following steps:

a. transmission of an electromagnetic field by the reader;

b. resonance of the resonant circuit of the transponder inducing thecontactless powering of the transponder, which is in a first state inwhich it does not allow the reading and/or writing of the memory andtransmits no datum or random data;

c. positioning of a portion of human body on a contact zone of thetransponder and switch to a second state of the transponder;

d. visual indication of the recognition of the positioning of a portionof human body on a contact zone of the transponder;

e. interchange of data between the memory of the transponder and thereader.

The interchange of data may comprise the sending of data relating to apayment and/or an authentication, and/or a digital signature to thereader, and/or the sending of other secure data.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

These objects, features and advantages of the present disclosure will beexplained in detail in the following description of particularembodiments made in a non-limiting manner with respect to the attachedfigures amongst which:

FIG. 1 represents schematically a transponder according to oneembodiment of the disclosure.

FIG. 2 represents schematically the electronic circuit of a transponderaccording to a first embodiment of the disclosure.

FIG. 3 represents schematically the electronic circuit of a transponderduring a transaction authorized by its holder according to the firstembodiment of the disclosure.

FIG. 4 represents schematically the electronic circuit of a transponderaccording to a first variant of the first embodiment of the disclosure.

FIG. 5 represents schematically the electronic circuit of a transponderaccording to a second variant of the first embodiment of the disclosure.

FIG. 6 represents schematically the electronic circuit of a transponderaccording to a third variant of the first embodiment of the disclosure.

FIG. 7 represents schematically the electronic circuit of a transponderaccording to a second embodiment of the disclosure.

FIG. 8 represents schematically the electronic circuit of a transponderduring a transaction authorized by its holder according to the secondembodiment of the disclosure.

FIG. 9 represents the top surface of an integrated circuit card of dualtype, with and without contact, according to one embodiment of thedisclosure.

FIG. 10 is a portable telephone according to one embodiment of thedisclosure.

DETAILED DESCRIPTION

The concept of the adopted solution is illustrated in FIG. 1. Itprovides a transponder 1 comprising a resonant circuit 2, including anantenna and a capacitor, at least one memory 5, a contact zone 8 forreceiving the contact of a portion of human body, and a visual indicator21. Without the contact of a user or similar conductive object on thecontact zone 8, a use of the transponder 1 is not possible, that is tosay more precisely that a data interchange between the memory 5 of thetransponder 1 and a reader is prohibited or degraded so that the normaluse of the transponder 1 to fulfill a certain application is notpossible. Therefore an intentional and precise action on the transponder1 enables its use, which removes the risk of fraudulent transactionwithout the knowledge of the holder of the transponder 1. Moreover, whensuch an intentional action has been recognized by the transponder, avisual indicator 21 indicates to its user that it is switching to ausage authorization state.

For the purposes of simplicity and clarity, the same references will beused in the various figures relating to various embodiments for similarelements.

FIGS. 2 and 3 represent a transponder 1 according to a first embodiment,which is shown as a contactless integrated circuit card of the paymentcard type.

The transponder 1 of FIGS. 2 and 3 comprises a resonant circuit 2,formed by an antenna and a capacitor, which form an oscillating circuitcomprising an inductor La placed in parallel with a capacitor Ca. Thisoscillating circuit is designed to capture a magnetic field generated bya reader. In the presence of a magnetic field the frequency of whichmatches the resonance frequency of the oscillating circuit of thetransponder 1, a voltage difference at the terminals 3 and 4 of theresonant circuit 2 is generated, which allows on the one hand thecontactless powering of the transponder and, on the other hand, theimplementation of a contactless data interchange between a memory 5 ofthe transponder 1 and the reader, via the resonant circuit 2 and anintermediate circuit 10 placed on the transponder, between its resonantcircuit 2 and the memory 5.

The terminals 3, 4 of the resonant circuit 2, which correspond to theterminals of the capacitor Ca, are linked to two terminals ofalternating input of a rectifier bridge consisting of four diodes D1,D2, D3, D4. As a variant, this diode bridge may be replaced by anequivalent device. A capacitor Cb is connected to the rectified outputterminals of high voltage 6 and low voltage 7 of the rectifier bridge soas to store energy and smooth the rectified voltage delivered by therectifier bridge. Thus, when the transponder is powered contactlessly bya reader, a voltage difference appears between its two terminals, thehigh terminal 6 and the low terminal 7. Then, the power supply voltageof the transponder, rectified by the rectifier bridge, smoothed by thecapacitor Cb, and regulated by a voltage regulator 27 (REG), powers theelectronic circuits of the transponder 1, including a microcontroller 28which manages the memory 5. As a variant, the upstream portion of theintermediate circuit 10, the function of which is a processing of thevoltage, could be different, simplified, for example according to thedisclosure of U.S. Pat. No. 7,995,965, which is incorporated herein byreference in its entirety.

An intermediate branch 34 connected between the two voltage terminals,high voltage 6 and low voltage 7, of the transponder, upstream of thevoltage regulator 27, comprises two contact pads 29, 30, situated closeto one another and forming an opening of this intermediate branch in afirst state of not authorizing the use of the transponder, representedin FIG. 2. A resistor R3 is also placed on this intermediate branch 34,of which a first intermediate terminal 33, situated between the contactpads 29, 30 and the resistor R3, is linked to a “visual indicator”device 20, which will be described below. A Zener diode 32 is placed inparallel with this resistor R3, between the intermediate terminal 33 andthe low-voltage terminal 7, in order to limit the maximum voltagereached at the intermediate terminal 33, which could cause damage to aswitch 26 of the “visual indicator” device 20 and to the input stage Dof a flip-flop 35.

A flip-flop 35 is placed between the intermediate terminal 33 and themicrocontroller 28, of which a synchronization clock input CLK is linkedto the clock of the microcontroller 28. The input D of the flip-flop 35is therefore linked to the potential of the intermediate terminal 33 andits output Q is linked to the microcontroller 28.

According to this first embodiment, the intermediate circuit 10 of thetransponder comprises a visual indicator device 20, linked to the highand low output terminals 6, 7 of the capacitor Cb. It comprises a visualindicator 21, in series with a first switch 22, between the twoterminals 6, 7 of the capacitor Cb, and two resistors R1, R2 in serieson a parallel branch between the high terminal 6 and the low terminal 7of the transponder of which one terminal of intermediate potential 25,between the two resistors R1, R2, is linked to the first switch 22 tocontrol its opening or its closure. Finally, a second switch 26 isplaced between the intermediate terminal 25 and the low-voltage terminal7. In this embodiment, these two switches are transistors of theN-channel MOS type. The positioning of the visual indicator device 20upstream of the voltage regulator 27 has the advantage of allowing it tooperate even in the event of insufficient voltage at the voltageregulator 27, or even of failure of the latter. However, as a variant,this visual indicator device 20 could be positioned differently withinthe intermediate circuit 10, for example downstream of the voltageregulator 27.

The operation of this transponder 1 according to the first embodimentwill now be explained. When there is no transaction, the transponder 1is for example in the pocket of its holder and its electric circuit isthat shown in FIG. 2. When it is not in the presence of anelectromagnetic field of a reader, the transponder receives no electricpower supply and therefore remains passive. When it is poweredcontactlessly by a reader, malicious or not, its resonant circuit 2 iscapable of beginning to resonate, when the transmission frequency of thereader matches its resonance frequency, and a potential difference maytherefore appear at the high and low terminals 6, 7 of the transponder.In this configuration, a high voltage appears at the first intermediateterminal 25 which induces the closure of the first switch 22, that is tosay making it conductive. The visual indicator 21, which may be a diodeof the LED type depending on the embodiment, then switches on,indicating that the transponder is powered contactlessly by a reader. Inthis configuration, the intermediate terminal 33 is not linked to thehigh voltage 6 of the transponder and the input D of the flip-flop takesa first low value (usually 0). Consequently, its output Q also takes alow value, received by the microcontroller 28, which interprets it as anunauthorized transaction situation. In such a case, the microcontroller28 is programmed to prohibit any data interchange between its memory 5and the reader, or even to transmit random unusable data to it. Thetransponder is therefore clearly in a first state of not authorizing itsuse. In this way, the security of the transponder is guaranteed and nofraud is possible without the knowledge of its holder. As a comment,this solution has the advantage that a reader can detect a transponder,since the latter begins to resonate, but cannot detect that it is atransponder fitted with a security solution as explained. This makes itpossible to prevent the defrauder from being informed of the detectionand of the neutralization of his attack.

If the holder of the transponder really wishes to carry out atransaction, he places a finger on the contact zone 8 arranged on thesurface of the transponder, so as to cover the two contact pads 29, 30,as shown in FIG. 3. This intentional action of the holder of the cardmodifies the electric circuit of the transponder by closing theintermediate branch 34, the intermediate terminal 33 of which then takesa higher voltage value sufficient to modify the output of the flip-flopQ to a second high value (usually 1), when the clock signal so allows,which is interpreted by the microcontroller 28 as an authorizedtransaction situation. Access to its memory 5 then occurs normally andthe planned application of the transponder is carried out securely. Thetransponder is then in a second state of authorizing its use.

As a comment, when the user removes his finger, the voltage of theintermediate terminal 33 is again modified, which makes the flip-flop 35return to its initial low state and again supply the microcontrollerwith an output signal Q at its first low value, which prohibits thetransaction. Thus, in this first embodiment as described, the user mustkeep his finger on the provided contact zone 8 throughout thetransaction.

At the same time, the voltage appearing at the first intermediateterminal 33 when the transponder 1 is in its state of authorizing itsuse, closes the second switch 26, that is to say that it makes itconductive so as to establish an electric connection between theintermediate terminal 25 and the low voltage 7 of the transponder, whichinduces the opening of the first switch 22. The visual indicator 21 thenswitches off and thus fulfils a second function indicating that thecommunication of the transponder is indeed authorized, that is to saythat the positioning of the finger of the user is indeed recognized bythe transponder.

As a comment, the positioning of the finger of the user on the contactpads 29, 30 forms an electric connection by the conductive property ofthe human body, which is equivalent to positioning a certain resistancebetween the two contact pads 29, 30. This phenomenon will be the sameirrespective of the portion of human body positioned on the two contactpads 29, 30. Advantageously, the two contact pads 29, 30 will bepositioned close to one another in order to allow them to be connectedwith a finger, even of small dimension.

FIG. 4 illustrates a first variant embodiment of the first embodiment,for which the circuit of the transponder is slightly modified to allow atransaction authorization by simple contact on the contact zone 8provided on the transponder, without requiring the finger to be kept onit throughout a transaction.

For this, the first intermediate terminal 33 of the electronic circuitis also connected to the low-voltage terminal 7 of the transponder by adiode D5 and capacitor Cc placed in series. The output Q of theflip-flop 35 is connected via an electric link 40, on which anotherdiode D6 is placed, to a terminal 41 of the capacitor Cc. The voltage ofthis terminal 41 is also connected to a third switch 42, placed inseries with a resistor between the high voltage 7 and low voltage 6 ofthe transponder downstream of the voltage regulator. An intermediateterminal 45 placed between this resistor and the third switch 42 drivesa fourth switch 43 similarly placed in series with a resistor betweenthe high voltage 7 and low voltage 6 of the transponder, delimiting anew intermediate terminal 46 connected to the input D of the flip-flop35.

The operation of this first variant execution will now be explained.When the transponder is positioned in an electromagnetic field at itsresonance frequency generated by a reader and the electric connection isobtained between the two pads 29, 30, by the positioning of a finger ofthe owner of the transponder on the appropriate contact zone 8, avoltage appears at the intermediate terminal 33 which induces theclosure of the third switch 42 and the setting to low voltage 7 of thevoltage of the intermediate terminal 45, which then opens the fourthswitch 43 in order to induce a high voltage of the intermediate terminal46 connected to the input D of the flip-flop. The latter then takes ahigh value and transmits an authorization signal to the microcontroller28. The contact of a finger on the provided contact zone 8 thereforecauses, in cascade, the closure of a switch 42 and the opening ofanother switch 43 in order finally to modify the state of thetransponder 1 to the second state for authorizing its use. In thisembodiment, the switches 42, 43 are transistors of the N-channel MOStype.

At the same time, the voltage on the intermediate terminal 33 causes thecharging of the capacitor Cc. In addition, the output voltage of theflip-flop is connected to the terminal 41 of this capacitor, which alsocauses its charging, which is maintained even when the finger is removedfrom the contact zone 8. Through this mechanism, the voltage forcontrolling the third switch 42 remains sufficient, through the chargingof the capacitor Cc, to keep the third switch 42 in the closed position,and by cascade effect, to keep the flip-flop in its configuration ofauthorizing a transaction, once there has been a simple contact on thecontact zone 8 provided for this purpose at the contact pads 29, 30. Asa comment, the diodes D5 and D6 then fulfill the function of preventingthe capacitor Cc from discharging. The simple non-permanent contact of aportion of human body is therefore sufficient in this variant execution,which is naturally possible notably by the fact that the transponderremains powered even after the finger of the user has been removed.

FIG. 5 illustrates a second variant of the first embodiment, whichcomprises a photodiode 23 (Dp) in series with a capacitor Cd, bothelements being placed between the two terminals, the high-voltageterminal 6 and the low-voltage terminal 7, of the transponder. Anintermediate terminal 24 placed between the photodiode 23 and thecapacitor Cd is connected to the second input of an AND logic gate 37,the output Q of the flip-flop 35 being connected to its first input.Finally, the output of the AND logic gate 37 is connected to themicrocontroller 28.

The operation of this second variant will now be explained. As above,the output Q of the flip-flop takes the second high value forauthorizing use of the transponder when the transponder enters theelectromagnetic field of a reader and when its holder authorizes thetransaction by touching the contact zone 8 provided for this purpose.However, in this embodiment, the final authorization to carry out thetransaction is not transmitted to the microcontroller 28, unless theadditional condition of the receipt of light by the photodiode 23 issatisfied, which has the effect of obtaining a higher voltage on theterminal 24, detected at the input of the AND logic gate 37. Thissolution makes it possible to prevent an unintended transaction, whichcould, for example, occur if a user, having, for example, histransponder 1 in his pocket, therefore in the dark, places his hand inhis pocket, unintentionally presses the contact zone 8 provided forauthorizing a transaction, and at the same time the transponder 1 ispowered contactlessly by a reader.

The above two variants comprise a visual indicator device 20 operatingin the same manner as in the embodiment described above with referenceto FIGS. 2 and 3.

FIG. 6 illustrates a third variant of the first embodiment, in which thevisual indicator function has been simplified. Specifically, the abovevisual indicator device 20 is removed and a visual indicator 21 issimply added to the channel 34 between the contact pads 29, 30 and theintermediate terminal 33. When a user authorizes a communication bypositioning a finger on the contact zone 8, the visual indicator 21lights up. In the other cases, it is off. For the rest, the operation ofthe transponder 1 remains equivalent to that explained above.

FIGS. 7 and 8 illustrate a second embodiment, in which the downstreamportion of the intermediate circuit 10, mainly placed between thevoltage regulator 27 and the microcontroller 28, is modified. First, achannel placed between the two terminals of voltage 6, 7 comprises aresistor R4 and a third switch 51, driven by the voltage of theintermediate terminal 25 defined by the visual indicator device 20 asexplained in the first embodiment. Moreover, the voltage of anintermediate terminal 53 on this channel, situated between the resistorR4 and the third switch 51, is connected to the input D of the flip-flop35. A channel 54 leaves the output of the flip-flop 35 and comprises adiode D8 and is then connected to the low voltage 7 of the transpondervia a capacitor Ce the cathode of which defines a terminal 52, whichdrives the second switch 26 of the visual indicator device 20. Finally,a contact pad 50 is provided on a contact zone 8, also connected to thisterminal 52, by a channel comprising a diode D7.

The operation of this second embodiment will now be explained. When thetransponder 1 is powered contactlessly by a reader, a voltage appears onthe intermediate terminal 25, which closes the third switch 51, thusplacing the voltage of the intermediate terminal 53 in connection withthe low voltage 7 of the transponder. The input D of the flip-flop 35 isthus connected to a low voltage and transmits as an output Q, at the lowvalue, a signal to the microcontroller 28 which is interpreted as thenon-authorization of the use of the transponder. The latter is thereforein a first state of not authorizing its use in its representation ofFIG. 7.

When a user positions a finger on the contact pad 50, as shown in FIG.8, he forms a capacitive effect which, by modifying the voltage value ofthe terminal 52, closes the second switch 26, placing the voltage of theintermediate terminal 25 in connection with the low voltage 7 of thetransponder. This value drives the opening of the third switch 51 and ahigh voltage appears at the intermediate terminal 53, transmitted as aninput D of the flip-flop 35, which allows the output Q of the flip-flop35 to take its high value, on the next rising (or falling) edge of theclock signal, and to take the second value, interpreted by themicrocontroller as the authorization of the transaction. At the sametime, the output voltage of the flip-flop makes it possible to maintainthe charge of the capacitor Ce at a sufficient value to keep the voltageof the terminal 52 at a value that keeps the second switch 26 closed,via the return channel 54 through the diode D8. The diodes D7 and D8then fulfill the function of preventing the capacitor Ce fromdischarging. In a variant embodiment, this capacitor Ce could be removedbecause the intrinsic capacitor (internal gate-source capacitor) of theN-channel MOS transistor forming the switch 26 could be sufficient tofulfill the same function.

Finally, a simple touch on the contact pad 50 by the user is enough toreach this second state of the transponder in which its communicationwith a reader is authorized. This state then remains stable, even if thefinger of the user is removed. As a comment, when this touch of the userhas been recognized, the voltage of the intermediate terminal 25 takesits low value and the first switch 22 opens causing the visual indicator21 to switch off, which thus indicates, as in the first embodiment, thatthe authorization of the user has been recognized.

In this second embodiment, the positioning of the finger of the user onthe contact pad 50 provides a certain charge to the pad 50, which, bycapacitive effect, makes it possible to charge a capacitor, for examplethe capacitor Ce in the embodiment shown in FIGS. 7 and 8. Thisphenomenon would be the same irrespective of the portion of human bodypositioned on the contact pad 50.

In the context of an implementation on an integrated circuit card, ofthe payment card type, which is thin, one or two contact pads made ofconductive material will be arranged in a surface layer of the card, ina contact zone 8, superposed on the contact pads of the electroniccircuit, in order to form an electric continuity and allow aninteraction of the user with the integrated circuit placed in anintermediate layer in the thickness of the card. To make the card easierto use, the contact zone 8 on which the user positions himself in orderto make the electric connection with the contact pad(s) and authorize atransaction will advantageously be made clear, for example, with the aidof a portion colored differently from the rest of the card, and/orcomprising a particular design, such as that of a finger, for example.

A dual card, that is to say a card that can operate with contact andwithout contact, in order to allow use by insertion into a reader for acommunication with contact by means of an electric connector, or a usewithout contact as described above, comprises a surface connector withcontact zones in a position and a geometry that are standardized. FIG. 9illustrates such a dual card 11 the connector 12 of which has eightcontacts C1 to C8, and an antenna not shown. In the particular case ofsuch a card, it is possible to make use of the presence of these surfacecontact zones to make it easier to implement the contact zone 8 designedfor authorization by its holder, as has been described in the precedingembodiments. As an example, FIG. 9 shows how the contact pad 50 of thecontact zone 8 can be arranged on the surface and connected to the restof the electric circuit by a simple connection to the contact C6 alreadyprovided on the card and not used in this embodiment, by means of aconnection 13 which makes it possible to place this contact zone 8 inthe desired location on the surface of the card. As a comment, a fewcontacts C1, C4, C5, C6, C8 are positioned on the circuits of thetransponders illustrated in FIGS. 2 to 8 to represent the electricconnection between the contacts concerned and the portions of theelectric circuit when the transponders 1 shown are in fact integratedcircuit cards. In the context of the first embodiment, it thereforeappears that the contact pads 29, 30 could be respectively connected tothe contacts C1, C6 of the card, for example.

Naturally, the embodiments described above can be easily adapted to alltypes of transponders which can occur in various formats, such ascontactless or dual integrated circuit cards and/or incorporated intoelectronic devices such as telephones, personal organizers, etc. In theparticular case of a device such as a telephone, the contact zone andthe indicator may be arranged within the casing of the device, or evenbe arranged within a screen that already exists on the device. Theadvantage of providing a contact zone and an indicator that areindependent is that it allows them to operate independently of thebattery of the device, even if this battery has no charge left.Moreover, the embodiments described can be implemented in transponderscommunicating according to the technology known as NFC (Near FieldCommunication), or more generally for short-distance contactlesscommunications at a frequency of between 10 and 15 MHz, or for anyinductive coupling. Moreover, such a transponder may or may not comprisean internal electric power supply, be intelligent, comprise one or moremicroprocessors, or comprise a much simpler structure of simple wiredlogic, more or less elementary, such as to form simple electroniclabels, often called electronic “tags”. Those skilled in the art willtherefore understand that the intermediate circuit 10 may take veryvaried forms depending on the type of transponder concerned.

The visual indicator can be a light-emitting diode (LED) or any othertype of visual indicator. As a variant, it can be an audible indicatoror any type of indicator. It may indicate that the positioning of aportion of human body on a contact zone provided for this purpose on thetransponder is or has been recognized by a continuous indication for aslong as the authorized communication lasts or by a shorter indication,limited in time. The transponder may comprise two distinct indicators,the first making it possible to indicate the recognition of thepositioning of a portion of human body on a contact zone provided forthis purpose on the transponder, and the second making it possible toindicate that the transponder is activated by the electromagnetic fieldof a reader.

The contact pads for receiving a portion of human body could be placeddifferently on the transponder, within the intermediate circuit 10between the resonant circuit 2 and the memory 5 of the transponder, oron the resonant circuit 2 or on the antenna itself. For example, thecontact pad 29 could be connected downstream of the voltage regulator27, in which case it is noted that the security Zener diode 32 wouldbecome unnecessary. Similarly the effect of transmitting authorizationto a microcontroller or any other component for access to a memory couldbe obtained by components other than a flip-flop, for example any otherdevice based on one or more logic gates. Moreover, the switchesimplemented in the embodiments described are transistors of theN-channel MOS type, but as a variant, there could be another type oftransistor, a P-channel transistor for example, or more generally anycomponent other than transistors fulfilling a switch function.

As a comment, the effects obtained and explained above by thepositioning of a portion of human body on a contact zone provided forthis purpose on the transponder are of resistive or capacitive type,that is to say that the portion of human body makes it possible to formeither an electric resistance or a capacitance or a contribution ofcharge, within the electronic circuit of the transponder, the firsteffect of which is to induce a change of voltage on a particularterminal of the transponder, and to modify the configuration of theelectronic circuit of the transponder to authorize a transaction. Asecond worthwhile effect consists in inducing a switching of a switch,as has been illustrated in the implementation examples described. Theseeffects are not very dependent on the electric properties of the portionof human body, do not require a precise value of resistance or ofcapacitance, and operate well in all conditions, with any person,irrespective of the ambient humidity, etc.

Finally, other execution variants may be imagined in the context of theconcept described, for example by the simple combination of theembodiments described above. Thus, the context of the protection soughtgoes beyond the embodiments described as examples and includesmodifications and enhancements.

For example, the above discussion describes contacting the contact zone8 with a portion of the human body in order to fully activate thetransponder 1, but one skilled in the art will recognize that otherobjects could be employed to contact the contact zone 8 and activate thetransponder 1. For example, the user could contact the contact zone 8using a conductive item, such as a capacitive stylus, or other devicecapable of changing the resistance or capacitance of the intermediatecircuit 10.

The disclosure also relates to a system comprising a reader, such as thereader 9 of Figure, furnished with an oscillating circuit at a certainresonance frequency and comprising a transponder as described above, theresonant circuit of which has a resonance frequency tuned to that of thereader, in order to be able to be powered contactlessly by the reader,power the transponder and allow a contactless communication.

The disclosure also relates to a method of contactless communicationbetween a reader and a transponder as described above, which comprisesthe following steps, according to one embodiment of the disclosure:

a. transmission of an electromagnetic field by the reader;

b. resonance of the resonant circuit of the transponder, which is in afirst state in which it does not allow the reading and/or writing of thememory and transmits no datum or random data;

c. positioning of a portion of human body on a contact zone of thetransponder and switch to a second state of the transponder;

d. visual indication of the recognition of the positioning of a portionof human body on a contact zone of the transponder;

e. interchange of data between a memory of the transponder and thereader.

This method of contactless communication can allow the interchange ofdata for carrying out, for example, a contactless electronic paymentand/or an authentication, and/or a digital signature sent to the readerand/or a simple secure data interchange.

One embodiment of the disclosure is a portable device, such as atelephone 60 as shown in FIG. 10. In FIG. 10, the telephone 60 is shownas including a touch screen 62 in addition to the transponder 1according to any of the embodiments disclosed herein, including thecontact zone 8. One skilled in the art will recognize that the contactzone 8 could be incorporated into a portion of the touch screen 62.

The various embodiments described above can be combined to providefurther embodiments. These and other changes can be made to theembodiments in light of the above-detailed description. In general, inthe following claims, the terms used should not be construed to limitthe claims to the specific embodiments disclosed in the specificationand the claims, but should be construed to include all possibleembodiments along with the full scope of equivalents to which suchclaims are entitled. Accordingly, the claims are not limited by thedisclosure.

1. A transponder comprising: a resonant circuit that includes an antennaand a capacitor; a memory; a contact zone configured to be contacted bya portion of human body; an enable/disable circuit configured to switchfrom a first state, in which the enable/disable circuit does not allowthe memory to be accessed, to a second state in which the enable/disablecircuit allows the memory to be accessed when the resonant circuit ofthe transponder is contactlessly powered by a reader; and a firstindicator configured to indicate that a portion of human body hascontacted the contact zone of the transponder.
 2. A transponderaccording to claim 1, comprising a second indicator configured toindicate that the transponder is contactlessly powered by a reader.
 3. Atransponder according to claim 1, wherein the first indicator is alsoconfigured to indicate that the transponder is contactlessly powered bya reader.
 4. A transponder according to claim 1, wherein the firstindicator is a visual indicator that includes a light-emitting diode. 5.A transponder according to claim 1, comprising: first and second supplyterminals; a first switch coupled in series with the first indicator ina first branch between the supply terminals; first and second resistorscoupled to each other in a second branch, parallel to the first branch,between the supply terminals, the resistors being coupled to each otherby an intermediate node that is also coupled to a control terminal ofthe first switch; and a second switch coupled between the intermediateterminal and the second terminal of the transponder.
 6. A transponderaccording to claim 1, wherein the indicator is electrically coupled tothe contact zone.
 7. A transponder according to claim 1, wherein theresonant circuit it is configured to be powered contactlessly around aresonance frequency that remains the same in both states of thetransponder.
 8. A transponder according to claim 7, wherein the resonantcircuit is configured to resonate and induce a voltage differencebetween the first terminal and the second terminal when the transponderis contactlessly powered by a reader, in both states of the transponder.9. A transponder according to claim 1, wherein the enable/disablecircuit and contact zone are part of an intermediate circuit coupledbetween the resonant circuit and the memory.
 10. A transponder accordingto claim 1, the contact zone includes a contact pad on which thepositioning of a portion of human body has a capacitive effect, orincludes two adjacent contact pads on which the positioning of a portionof human body has a resistive effect.
 11. A transponder according toclaim 1, wherein the enable/disable circuit is configured to switch fromthe first state to the second state in response to a portion of humanbody being placed on the contact zone and is configured to remain in thesecond state after the portion of human body is removed from the contactzone.
 12. A transponder according to claim 1, wherein the transponder isa contactless or dual integrated circuit card.
 13. A telephone,comprising: a transponder that includes: a resonant circuit thatincludes an antenna and a capacitor; a memory; a contact zone configuredto be contacted by a portion of human body; an enable/disable circuitconfigured to switch from a first state, in which the enable/disablecircuit does not allow the memory to be accessed, to a second state inwhich the enable/disable circuit allows the memory to be accessed whenthe resonant circuit of the transponder is contactlessly powered by areader; and an indicator configured to indicate that a portion of humanbody has contacted the contact zone of the transponder.
 14. A telephoneaccording to claim 13, wherein the indicator is also configured toindicate that the transponder is contactlessly powered by a reader. 15.A telephone according to claim 13, wherein the indicator is a visualindicator.
 16. A telephone according to claim 13, comprising: first andsecond supply terminals; a first switch coupled in series with the firstindicator in a first branch between the supply terminals; first andsecond resistors coupled to each other in a second branch, parallel tothe first branch, between the supply terminals, the resistors beingcoupled to each other by an intermediate node that is also coupled to acontrol terminal of the first switch; and a second switch coupledbetween the intermediate terminal and the second terminal of thetransponder.
 17. A telephone according to claim 13, wherein theenable/disable circuit is configured to switch from the first state tothe second state in response to a portion of human body being placed onthe contact zone and is configured to remain in the second state afterthe portion of human body is removed from the contact zone.
 18. A systemcomprising: a reader configured to oscillate at a resonance frequency;and a transponder that includes: a resonant circuit having a resonancefrequency substantially equal to the resonance frequency of the reader;a memory; a contact zone configured to be contacted by a portion ofhuman body; an enable/disable circuit configured to switch from a firststate, in which the enable/disable circuit does not allow the memory tobe accessed, to a second state in which the enable/disable circuitallows the memory to be accessed when the resonant circuit of thetransponder is contactlessly powered by a reader; and an indicatorconfigured to indicate that a portion of human body has contacted thecontact zone of the transponder.
 19. A system according to claim 18,wherein the indicator is also configured to indicate that thetransponder is contactlessly powered by a reader.
 20. A system accordingto claim 18, wherein the indicator is a visual indicator.
 21. A systemaccording to claim 18, comprising: first and second supply terminals; afirst switch coupled in series with the first indicator in a firstbranch between the supply terminals; first and second resistors coupledto each other in a second branch, parallel to the first branch, betweenthe supply terminals, the resistors being coupled to each other by anintermediate node that is also coupled to a control terminal of thefirst switch; and a second switch coupled between the intermediateterminal and the second terminal of the transponder.
 22. A systemaccording to claim 18, wherein the enable/disable circuit is configuredto switch from the first state to the second state in response to aportion of human body being placed on the contact zone and is configuredto remain in the second state after the portion of human body is removedfrom the contact zone.
 23. A method of contactless communication betweena reader and a transponder, the method comprising: transmitting anelectromagnetic field by the reader; contactlessly powering thetransponder using the electromagnetic field, based on a resonance of theresonant circuit of the transponder, the transponder having a firststate in which a memory is inaccessible to the reader; switching to thesecond state in response to a conductive object being positioned on acontact zone of the transponder; visually indicating a recognition ofthe positioning of the conductive object on the contact zone of thetransponder; interchanging data between the memory of the transponderand the reader while the transponder is in the second state.
 24. Amethod of contactless communication according to claim 23, whereininterchanging data comprises sending data relating to a payment and/oran authentication, and/or a digital signature to the reader, and/or thesending of other secure data.